diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 78b1ae0..9aa07a1 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -582,7 +582,7 @@
 					// Users can use any native PHP function call that has one param.
 					if (function_exists($rule))
 					{
-						$result = $rule($postdata);
+						$result = ($param !== FALSE) ? $rule($postdata, $param) : $rule($postdata);
 
 						if ($_in_array === TRUE)
 						{